Quote:
Originally Posted by sheeny
From an engineering point of view don't do it.
Adding the sand adds mass which lowers the natural frequency of your pier.
For a given vibration energy, a high frequency vibration has a smaller amplitude than a low frequency vibration. Adding the sand gives a larger amplitude of vibration than without it.
There may be anecdotal evidence that sand filling helps to dampen the vibration more quickly, but that's of little value if the first movement is enough to blur your image anyway.
When I did the calcs for my pier (100SHS about 900 tall) the amplitude of vibration increased about 4.5 to 5 times over the empty pier, so it was clear to me it's an old wives tale.
I know there are experts here who know more about engineering than a professional engineer does... so I wish you luck deciding. 
Al. |
G'day Al,
Would filling the pier with grout make the whole thing more rigid and less prone to vibration in the first place? I understand that anything will vibrate if you hit it hard enough or fast enough, but short of hitting it with a truck I'd imaging the pier in question would be pretty solid.
I've been entertaining the idea of building a pier for some time now and couldn't resist the opportunity to pick an engineers brain. Sorry to the OP for chiming in with more Q's.